Maximum MTU/MRU values in GWN7000 network interfaces

Improper MTU/MRU settings will lead to fragmentation and will directly affect the network transmission speed. Here is the max value for each type of transport in GWN7000

Ethernet MinSize = 512bit = 64 Byte

Ethernet MaxSize = 1518 Byte

so Ethernet IP MTU = 1518 - 18 ( 6 SRCMAC+ 6 DSTMAC+ 2 TYPE+ 4 CRC) = 1500 B

so Ethernet IP TCP MSS = 1500 - 40 ( 20 IP_HEADER + 20 TCP_HEADER) = 1460 B

so Ethernet IP UDP MTU/MRU = 1500 - 28 ( 20 IP_HEADER + 8 UDP_HEADER ) = 1472 B

so PPPoE MTU/MRU = 1500 - 8 ( 6 PPPoE_SESSION + 2 PPP_HEADER ) = 1492 B

so TCP over PPPoE MSS = 1492 ( PPPoE MTU/MRU ) - 40 ( 20 IP_HEADER + 20 TCP_HEADER) = 1452

so PPTP MTU/MRU = 1500 - 56 ( 20 IP_HEADER + 20 TCP_HEADER + 12 GRE_HEADER + 4 PPP_HEADER ) = 1444 B

so TCP over PPTP MSS = 1444 ( PPTP MTU/MRU ) - 40 ( 20 IP_HEADER + 20 TCP_HEADER) = 1404

so L2TP MTU/MRU = 1500 - 40 ( 20 IP_HEADER +8 UDP_HEADER + 8 L2TP_HEADER + 4 PPP_HEADER ) = 1460 B

so TCP over L2TP MSS = 1460 ( L2TP MTU/MRU ) - 40 ( 20 IP_HEADER + 20 TCP_HEADER) = 1420 B

so PPTP over PPPoE MTU/MRU = 1492 ( PPPoE MTU/MRU ) - 56 ( 20 IP_HEADER + 20 TCP_HEADER + 12 GRE_HEADER + 4 PPP_HEADER ) = 1436 B

so PPTP over PPTP MTU/MRU = 1444 ( PPTP MTU/MRU ) - 56 ( 20 IP_HEADER + 20 TCP_HEADER + 12 GRE_HEADER + 4 PPP_HEADER ) = 1388 B

so PPTP over L2TP MTU/MRU = 1460 ( L2TP MTU/MRU ) - 56 ( 20 IP_HEADER + 20 TCP_HEADER + 12 GRE_HEADER + 4 PPP_HEADER ) = 1404 B

so L2TP over PPPoE MTU/MRU = 1492 ( PPPoE MTU/MRU ) - 40 ( 20 IP_HEADER +8 UDP_HEADER + 8 L2TP_HEADER + 4 PPP_HEADER ) = 1452 B

so L2TP over PPTP MTU/MRU = 1444 ( PPTP MTU/MRU ) - 40 ( 20 IP_HEADER +8 UDP_HEADER + 8 L2TP_HEADER + 4 PPP_HEADER ) = 1404 B

so L2TP over L2TP MTU/MRU = 1460 ( L2TP MTU/MRU ) - 40 ( 20 IP_HEADER +8 UDP_HEADER + 8 L2TP_HEADER + 4 PPP_HEADER ) = 1420 B

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